With the development of more and more sophisticated electronic components, relatively extreme temperatures can be generated. This is clearly true with respect to electronic components capable of increasing processing speeds and higher frequencies, having smaller size and higher power density requirements, those generating new lighting advancements or exhibiting other technological advances. These components include microprocessors and integrated circuits in electronic and electrical devices and systems as well as in other devices such as high power optical devices. However, microprocessors, integrated circuits and other sophisticated electronic components typically operate efficiently only under a certain range of threshold temperatures. The excessive heat generated during operation of these components can not only harm their own performance, but can also degrade the performance and reliability of the overall system and can even cause system failure. The increasingly wide range of environmental conditions, including temperature extremes, in which electronic systems are expected to operate, exacerbates these negative effects.
With the increased need for heat dissipation from electronic devices caused by these conditions, thermal management becomes an increasingly important element of the design of electronic products. As noted, both performance reliability and life expectancy of electronic equipment are inversely related to the component temperature of the equipment. For instance, a reduction in the operating temperature of a device such as a typical silicon semiconductor can correspond to an exponential increase in the reliability and life expectancy of the device. Therefore, to maximize the life-span and reliability of a component, controlling the device operating temperature within the limits set by the designers is of paramount importance.
Electronic components are typically mounted to a circuit board, also known as a printed circuit board (PCB). The PCB has electrically conductive elements arranged to form an electrical circuit. With traditional PCBs, such as FR4 PCBs, and metal core printed circuit boards (“MCPCB”), the electrically conductive elements are arranged on a substrate. An example of a conventional substrate include fiber reinforced boards, commonly used as FR4 PCBs. Another example of a conventional substrate is a metal base layer, such as for example aluminum, copper, or other known metal which are typically used in MCPCBs and IMSPCBs. Another example of a conventional substrate is ceramics and ceramic compositions.
It is desirable to improve the thermal management of circuit boards to address the needs discussed above.
A liquid crystal display, or LCD, is a display apparatus that utilizes an image display panel formed of two transparent sheets of polarizing material separated by a liquid containing rod-shaped crystals where the polarizing axes of the two sheets are aligned perpendicular to each other. The LCD is constructed to display an image by passing an electric current through the liquid that causes the crystals to align to block light. Each crystal can be controlled individually and acts like a shutter. When the current is applied to specific pixel-like areas, those crystals align to create dark area, or images. The dark areas are combined with light areas to create text and images on the panel. LCD panels do not emit light. Instead, they control how light which is emitted from an external source passes through the LCD and onto the screen to form an image. LEDs are typically used as the light source. The LCDs are back-lit or side-lit by the LEDs depending on the arrangement used.
As manufacturers continually improve the performance of LCD displays, such as by increasing the display's brightness, ever-brighter LEDs are being utilized. As a result, the power consumption of the LEDs has increased substantially. LEDs convert at least 70% of their power to heat. The heat generated in the light source is detrimental to the operation and viewing of a liquid crystal display. The light source discharge heat that is transferred to the image display panel, other electrical components in liquid crystal display, and the support structure of the liquid crystal display. Indeed, some of the electrical components in the display panel are themselves heat sources, which compounds the problem. However, these other components of the liquid crystal display normally possess poor thermal spreading properties and are not normally designed to dissipate heat away from the light source, especially in directions parallel to the image display panel face.
In addition, the illuminating light of a liquid crystal display remains in an energized state and at a consistent power level regardless of the image characteristics on the viewing panel. Variances in the image are control by the arrangement and alignment of the crystals in the image display panel. As such, the components of the liquid crystal display are in need of relief from the constant heat generated by the illuminating light. The constant heat generation can accelerate thermal deterioration of the liquid crystal material from which the display is formed and shorten the useful lifespan of the liquid crystal display device. Heat may also negatively affect the refresh rate of the screen.
Conventional display devices typically utilize a thick, heavy metal support member (often a thick aluminum sheet, or set of multiple sheets) to which is attached both the display panel unit, the light source (which, in the case of LEDs, may be mounted to printed circuit boards, such as a metal core printed circuit board (MCPCB) with a thermally conductive dielectric material) and associated electronic components. Heat passing from these heat sources contributes to uneven temperature distributions created on the panel unit itself, which adversely affects the image presented on the display panels as well as display panel reliability.
The conventional support member provides both a mechanical function (i.e., for mounting the panel unit and associated electronics), as well as a thermal function (i.e., to help sink and spread heat generated by the light source(s) and/or the associated electronics). Accordingly, the support member is typically fabricated from a solid sheet of aluminum, on the order of about 2.0 mm thick. It will be recognized that, since most metals are relatively thermally isotropic, the in-plane thermal conductivity is not substantially different from the through-plane thermal conductivity of the material.
LCD device manufacturers are under extreme pressure to reduce the cost and weight of their existing display solutions, while there has simultaneously been a desire to increase the brightness and luminous efficiency of the panel units. This can mean more power being sent to the light sources, which increases the thermal load on the system and requires additional heat dissipation capabilities within the display units. In addition to increasing brightness and luminous efficiency of the displays, display manufacturers are also under increasing pressure to produce larger panel sizes, which tends to increase the weight of the frame system (especially the support member) proportionately.
Thus, what is desired is a light weight and cost effective system for display devices which provides enhanced heat transfer capabilities for the light source circuits.